Content Delivery Network or Content Distribution Network, CDN – geographically distributed network infrastructure which allows optimizing delivery and distribution of content to the end network users (source).
Who needs to use CDN and why?
CDN is used in web-portal development. Firstly, it reduces the load on their own servers – static files will give away CDN servers. Secondly, it will increase download time of your application for a user – data will be downloaded from the nearest CDN-server, i.e. through the shortest network route.
1) Amazon: every 100 ms download slowdown of a page will decrease the number of sale by 1 % (Source: Greg Linden, Amazon)
2) Google: 500 ms data results slowdown cause 20% loss of search requests.
3) Yahoo!: 400 ms of additional time for page loading cause for 5 to 9% increase of number of users that pushed “back” button before the end of loading. (Source: NicoleSullivan, Yahoo!)
Therefore, page loading speed is important! :)
CDN & Drupal
To integrate CDN infrastructure into Drupal sites, we use the CDN module.
For module installation and setting we need to:
1) apply patch to the core if you use Drupal 6 (Pressflow version and Drupal 7 already have this patch in core)
2) connect to one (or more) CDN networks (the most popular are VoxelCAST, Akamai, Amazon…)
3) fill in the field CDN MAPPING on page /admin/settings/cdn/details.
For all the files to be downloaded from one CDN server, just write a route to it, e.g. «cdn.example.com».
4) turn on CDN usage (route - /admin/settings/cdn,radiobutton status)